The present disclosure relates to a display element which emits a light by utilizing an organic electro luminescence (EL) phenomenon, a display device including the same, and an electronic apparatus including the display device.
Although an organic EL element attracts attention as a major candidate of next-generation display elements, it becomes a problem that a luminous efficiency is low and a life is short.
The life of the organic EL element (display element) generally depends on the electric charges injected, and the life characteristics can be improved by reducing an initial luminance in drive. However, by reducing the initial luminance, as a result, an application in practical realization is limited, and the potential possibility of the display element is negated by the organic EL element itself. For this reason, it is necessary to realize an element structure in which the luminance can be increased without changing a drive current, that is, the luminous efficiency can be improved, or the same luminance can be obtained even when the drive current is reduced.
Under such circumstances, a stack type multi-photo emission element (MPE element) has been proposed. For example, Japanese Patent Laid-Open No. Hei 11-329748 proposes an element in which plural organic layers including at least a light emitting layer are electrically joined in series with one another through a connection layer (intermediate conductive layer).
In addition, Japanese Patent Laid-Open Nos. 2003-45676 and 2003-272860 each disclose a concrete element structure for realizing the MPE element. According to Japanese Patent Laid-Open Nos. 2003-45676 and 2003-272860, it is described that theoretically, the lamination of two light emission units can improve a luminous efficiency (cd/A) without changing an electric power efficiency (lm/W) by a factor of 2, and the lamination of three light emission units can improve the luminous efficiency (cd/A) without changing the electric power efficiency (lm/W) by a factor of 3.